Well tools



WELL TOOLS Sheet Filed Dec. 1, 1966 S 9 R L w w mm W 2 w m w E O H w MBP W A a HE A w m G F IUDI/ 8 m a A W 54 55 2 2 Q m Y m m 2/ B w w 7% Z 2 9 F m 6 F 2 a Feb. 18, 1969 J. H. BOSTOCK ETAL 3, 7,989

WELL TOOLS Filed Dec, 1, 1966 Sheet 2 of 5 Fig.4

INVENTORS James H. Bosfock Ffhillip E. Pierce Feb. 18, 1969 .v H. BosTocK ETAL 3,427,989

WELL, TOOLS Sheet 3 of 5 Filed Dec. 1, 1966 1 I I I f ENT 5 James H. Bosfo Phillip E. Pierce W W Wm Feb. 18, 1969 J. H. BOSTOCK E-TAL WELL TOOLS Filed Dec. 1, 1966 Feb. 18, 1969 J. H. BOSTOCK ETAL 3,4 7,

WELL TOOLS Sheet Filed Dec. 1, 1966 w m w m 9 S M w 56% M HE m b c SW...

W W c r 55? W Q 9 JP 0% L? N United States Patent 3,427,989 WELL TOOLS James H. Bostock, Dallas, and Phillip E. Pierce, Carrollton, Tex., assignors to Otis Engineering Corporation, Dallas, Tex., a corporation of Delaware Filed Dec. 1, 1966, Ser. No. 598,490

US. Cl. 103-232 Int. Cl. F04f 1/20 25 Claims ABSTRACT OF THE DISCLOSURE This invention relates to well tools and more particularly to well installations having means for injecting gas into a flow conductor to facilitate production of well fluids therethrough and to means for controlling the injection of gas into a flow conductor.

An object of this invention is to provide a new and improved well installation having a flow conductor through which well fluids are transportable to the surface of a well and means for controlling injection of lift gas into the flow conductor from an annulus thereabout.

Another object is to provide a well installation of the type described wherein the means for controlling injection of the lift gas is responsive to the pressure in the flow conductor adjacent the location of injection, and therefore, the height of the well fluids above the location of injection, and causes injection of the gas when such column of well fluids attains a predetermined height.

Still another object is to provide a well installation of the type described wherein the value of the pressure at the location of injection of the gas at which the injection is caused to occur may be varied by meanslocated at the 7 surface of the well.

A further object is to provide a well installation of the type described which includes means for stopping injection of the gas into the flow conductor when the upper end of the column of well fluids reaches the upper end of the flow conductor so that expansion of the injected gas will compete the lifting of the well fluids from the well.

A still further object is to provide a well installation of the type described which includes a valvemounted onthe flow conductor and having a passage through which the lift gas from the annulus is injectable into the flow conductor, a closure member biased toward closed position closing the passage, means for communicating the pressure from the annulus to the closure member for moving the closure member to open the passage, and electrically operable valve means for controlling the admission of the fluid pressure from the annulus to the closure member.

Another object is to provide a well installation of the type described which includes a transducer responsive to the fluid pressure in the flow conductor adjacent the valve which varies the resistance of the electric circuit in which the solenoid coil of the valve is connected to cause the solenoid to open the valve when the pressure within the flow conductor at the transducer attains a predetermined value, and, therefore, the column of well liquids in the flow conductor above the valve attains a predetermined height.

Still another object is to provide a well installation of the type described wherein the electric circuit includes a variable resistance at the surface whereby the value of pressure within the flow conductor at the transducer at which the solenoid main valve is caused to open may be varied as desired.

Another object is to provide a new and improved valve for use in a well installation of the type described which includes a housing mountable on the flow conductor and having a passage for transmitting the lift gas from the annulus into the flow conductor, a closure member biased to position closing the passage, and a solenoid operable when the current flowing through its coil rises to a predetermined value for causing the pressure from the exterior of the housing to be exerted on a piston means to move the closure member to open position.

Still anther object is to provide a new and improved transducer having a pressure responsive means, such as a bellows, for moving a contact of a variable resistance in accordance with the pressure in a flow conductor to vary the value of the resistance.

A further object is to provide a well installation having a flow conductor through which well fluids are transportable to the surface of the well and having spaced valves for selectively injecting gas into the flow conductor at any one of the valves.

A still further object of the invention is to provide a well installation wherein the operation of the valves is controllable at the surface of the well.

A further object is to provide a well installation wherein the valves are operable in response both to the pressure within the flow conductor at the locations of the valves and also to the pressure of the lift gas.

Still another object is to provide a well installation wherein the control means permits operation of the valves only if the pressure of the gas applied to the well installation is above a predetermined value.

Additional objects and advantages of the invention will be readily apparent from the reading of the following description of a device constructed in accordance with the invention, and reference to the accompanying drawings thereof, wherein:

FIGURE 1 is a vertical partly sectional schematic View of an installation embodying the invention;

FIGURE 2 is a schematic partly sectional view showing the electric circuit of the well installation;

FIGURE 3 is a vertical partly sectional view of the upper portion of the main valve of the well installation;

FIGURE 4 is a view similar to FIGURE 3, being a continuation thereof, and showing the lower portion of the main valve;

FIGURES 5, 6 and 7 are vertical partly sectional view taken on lines 5-5, 6-6 and 77, respectively, of FIG- URE 3;

FIGURE 8 is a vertical partly sectional view of the upper portion of the transducer of the well installation;

FIGURE 9, is a vie-w similar to FIGURE 8, being a continuation thereof, showing the lower portion of the transducer;

FIGURE 10, is a schematic view of a modified form of the electric circuit of the well installation; 7

FIGURE 11 is a schematic vertical partly sectional view of a modified form of the well instalaltion embodying the invention;

FIGURE 12 is a fragmentary partly sectional view of a modified. form of the valve embodying the invention usable in the well installation illustrated in FIGURE 11;

3 view of another modified form of the well installation embodying the invention; and,

FIGURE 17 is a schematic illustration of the electric circuit of the well installation illustrated in FIGURE 16.

Referring now particularly to FIGURES 1 through 9 of the drawings, the well installation 20 embodying the invention, for introducing gas under pressure into an annulus A between a well casing 21 and a string of tubing or flow conductor 22 above a barrier or packer 23 which seals between the production flow conductor and the casing and for injecting the gas into the production flow conductor to facilitate the production of well fluids, includes an electrically operated main valve 25 mounted on the production flow conductor which controls the injection of gas from the annulus into the production flow conductor and a control device or transducer 26 which in turn controls the operation of the main valve. The transducer is responsive to the pressure within the production flow conductor at a location adjacent the main valve to cause the main valve to open whenever a column of well liquids in the flow conductor attains a predetermined height above the transducer. The well fluids flow from a producing earth formation penetrated by the well into the casing below the packer through the perforations in the casing, not shown, at such earth formation and then upwardly into the open lower end of the production flow conductor. The well installation may also include one or more suitable vertically spaced gas lift valves 27 for unloading the annulus above the packer and the production flow conductor of well liquids upon initiation of production of well liquids.

Gas under pressure is introduced into the annulus through a supply conduit 28 connected to the usual casing head 29 of the well installation at the surface of the well. The production flow conductor which extends upwardly through the casing head has a flow conduit 30 connected thereto through which the produced well fluids, as well as the gas introduced into the production flow conductor through the gas lift valves 27 or the main valve, are conducted to locations of storage or use.

The main valve, FIGURES 2 through 6, is mounted on a section 32 of the production flow conductor or string of tubing which is connected at its opposite ends to adjacent tubing sections between which it is located and to which it is connected by the usual coupling collars 33. A mount ring 34 rigidly secured to the tubing section 32, as by welding, has a lateral port 36 which communicates between a lateral port 37 of the tubing section and the central bore or passage 38 of the mount ring. A tubular valve housing 40 is secured to the mount frame, the reduced upper end portion 41 of its top section being threaded in the enlarged lower portion of the ring passage 38. An O-ring 43 seals between the top valve housing section and the ring. The bottom section 45 of the valve housing has a reduced top end portion 46 threaded in the lower end portion of the top section.

The bottom housing section has a plurality of slots or ports 47 and the top housing section has an upwardly and inwardly beveled annular seat surface 48 engageable by a seal ring 49 of a valve or closure member 50 to prevent upward flow of well fluids, which may enter into the valve housing through its ports 47, through the valve housing to the passage 38 of the mount ring and thence through the lateral ports 36 and 37 of the ring and tubing section into the longitudinal flow passage of the tubing section. The O-ring 49 is held between a downwardly facing shoulder 51 of the closure member and a retainer ring 53 disposed on a reduced portion of the closure member. The retainer ring is held against downward movement by the nuts 56 threaded on the reduced lower end portion 57 of the closure member. The retainer ring is provided with a plurality of passages through which liquid or gas trapped below the O-ring may escape as the retainer ring is moved upwardly into engagement with the O-ring during the assembly of the elements of the closure member. Upward movement of the closure member in the valve housing is limited by the engagement of its upwardly facing downwardly and outwardly inclined annular shoulder 59 with the seat 48 of the valve housing.

The bottom valve housing section provides an annular seat 60 which is engageable by the seat surface 62 of a check valve 63 which prevents downward flow through the valve housing. The check valve has dependent lower portion 64 which helps center it in the valve housing and provides the required mass or means for biasing the check valve to its lower closed position in the valve housing. The check valve has a bumper or shock absorbing resilient pad or rubber 56 or the like, the lower portion of the pad being disposed in an upwardly opening recess in the top end of the check valve and being bonded or ad-hesively secured thereto. The bumper pad is engageable with the lower end of the closure member to cushion or absorb the shock between the closure member and the check valve as the check valve moves upwardly when the closure member is moved downwardly to permit flow of gas from the annulus into the tubing section 32.

The shank 68 of the closure member extends upwardly through the passage 38 of the mount ring into an operator housing 70 whose bottom section 71 has a reduced end portion 72 threaded in the top enlarged portion of the mount ring passage 38. An O-ring 73 seals between the operator housing bottom section and the mount ring. The closure member is biased to its upper closed position by a spring 77 disposed about the closure member, the lower end portion of the spring bearing against the upwardly facing annular shoulder 78 of an internal annular flange 79 of the bottom operator housing section and the upper end portion of the spring bearing against the annular bottom surface of a piston ring 80 threaded on the top reduced end portion 81 of the closure member. Downward movement of the piston ring on the closure member is limited by the engagement of its bottom end surface with an upwardly facing annular shoulder 82 of the closure member. A seal ring 85 disposed about the closure member seals between the piston ring and the closure member, the seal ring being compressed by a nut 86 threaded on the top end portion 81. A lock nut 86 is also threaded on the top end portion of the closure member to prevent accidental displacement of the nut.

A pair of O-rings 89 which sealingly engage the internal seal surface 90 of the middle operator housing section 91 seals between the piston ring and the operator housing. A sleeve 94 slidably telescoped in the operator housing bottom section has an external annular flange 95 which extends above the top annular end surface 96 of the bottom operator housing section. A resilient annular bumper pad 99 is interposed between the flange 95 and the end surface 96 and yieldably opposes downward movement of the sleeve 94 when the closure member is moved downwardly to its lower open position and the piston ring engages the flange 95. The middle operator housing section is threaded on the upper end portion of the bottom section. The middle section 91 provides a chamber 100 above the piston ring to which is communicated the pressure of lifting gas from the annulus when the armature 101 of a solenoid assembly 102 is moved to its upper position.

The solenoid assembly is secured to the top operator housing section 104 which in turn is rigidly secured to the middle operator housing by a plurality of bolts 105 wihch extend through apertures 106 of the middle housing section into aligned downwardly opening bores in the top housing section. The middle operator housing section has a lateral port 110 which opens to the annulus A and a vertical port 111 which is in communication with the lateral port 110 with the vertical port 112 of the top housing section. A seat ring 113 having restricted orifice is secured as by a press fit in the top enlarged portion of the passage 112 and is closed when the armature is in its lower position by the resilient seat 115 molded in a downwardly opening bore of the body. The orifice of the seat ring 113 opens to the enlarged upwardly opening recess 116 of the top housing section, when the armature is raised, to permit the pressure of the lift gas from the exterior of the valve to be communicated through the communicating passages 117 and 118 of the top and middle operator housing sections into the chamber 100. The top housing section has a downwardly opening recess in which is disposed an O-ring 119 which seals between the top and middle operator housing sections at the location of communication of the passages 117 and 118, and also downwardly opening recess in which is disposed an O-ring 120 which seals between the two operator housing sections at the location of communication of the passages 112 and114 thereof. It will be apparent that when the armatures move upwardly the pressure of the lift gas from the annulus communicated to the chamber 100 tends to move the closure member 50 downwardly to its open position.

The solenoid assembly 102 includes a core member of a non-magnetic substance having a bottom external annular flange 126 which is threaded in a suitable upwardly opening recess 127 of the top operator housing section and about which is disposed the solenoid coil 128. A protective case 130 extends about the solenoid coil with its lower end portion telescoped over an annular upward extension 131 of the top operator housing section and is held against upward displacement by a nut 133, threaded on the upper reduced end portion 134 of the core, which engages the top surface of the case. The electric conductors 135 and 136 connected to opposite ends of the solenoid coil extend fromthe case through a grommet 136a.

The core has a downwardly opening bore 137 in which the upper portion of the armature is movable. The armature is biased toward its lower closed position by gravity and by a spring 140 disposed about the armature whose upper end portion bears against the bottom end surface of the solenoid core 125 and whose bottom end portion bears against the upper top annular surface of an external annular flange 141 of the armature.

The solenoid core has a longitudinal pressure relief passage 144 therethrough which is closable by a resilient seat 145 molded in a bore in the top end of the armature, when the armature is moved to its upper position and the seat engages the annular seat surface 147 of the core which extends about the lower reduced end of the core passage. The upper end of the core passage communicates with the longitudinal passage of the tubing section through a coupling collar 149 which connects the upper end of the solenoid core to a tube 150, the longitudinal passage 151, the lateral port 152, the annular external recess 153 of the tube and the ports 155 and 156 of a lug 157 and the tubing section 32, respectively. The upper end portion of the tube is telescoped in the longitudinal passage 158 of the lug 156 to which the port 155 opens and is provided with a pair of O-rings 159 and 160' disposed in suitable external annular recesses of the tube which seal between the tube and the lug 156 above and below, respectively, the port 155 and the recess 153.

Referring now particularly to FIGURES 7 and 8 of the drawings, the transducer 26 includes a housing having a bottom section 171 whose reduced lower end portion 172 is threaded in an upwardly opening bore 173 of a port lug 174 secured, as by welding, to the tubing section 32. The port lug 174 has a passage 175 which communicates with the longitudinal passage 176 of the bottom housing section and with a lateral port 177 of the tubing section 32 so that the pressure in the tubing is communicated to the exterior of a bellows assembly 180 located in a bellows section 181 of the housing. The lower reduced end portion 182 of the bellows housing section is threaded in the upper end portion of the bottom housing section.

The bellows assembly 181 includes an elongate rod 184 which is biased downwardly by a spring 186 whose top end portion engages the bottom surface of a retainer ring 187 rigidly secured, as by welding, to the bellows housing section. The retainer ring rests on an internal upwardly facing shoulder 188 of the bellows housing section. The bottom end portion of the spring bears against an adjusting nut 190 threaded on the bellows rod so that the force with which the spring biases the bellows rod downwardly may be adjusted by adjusting the position of the nut on the lower threaded end portion of the bellows rod. A lock nut 191 looks the adjusting nut against rotation from its adjusted position on the bellows rod. The bellows assembly also includes a lower resilient bellows section 192 whose bottom end is secured to a retainer ring 193 which in turn is secured to an external annular flange 194 of the bellows rod. The upper end of the lower bellows section is secured to a top retainer ring 195. The upper bellows section 196 has its lower end portion secured to a bottom retainer ring 197 which is secured to the top retainer ring of the lower bellows section. The upper end of the upper bellows section is secured to a top retainer ring 198 which in turn is secured to the lower end of the connector section 199 of the housing. The connector section has a lower reduced portion threaded in the upper end of the bellows housing section and a dependent annular flange 200 which is received in annular upwardly opening recess of the upper retainer ring 198. The bellows sections: are secured to their retainer rings, the retainer rings 195 and 197 are secured to one another, the bottom retainer ring is secured to the bellows rod flange 194 and the retainer ring 198 is secured to the connector housing section by silver solder, welding, and the like, which provides a gas tight seal or connection therebetween.

It will be apparent that due to the connection of the bellows sections and retainer rings to one another and to the piston rod and the connector housing section by silver solder, welding and the like, which provides a seal therebetween, the bellows assembly provides a resilient connection between the bellows rod and the housing which permits upward movement of the bellows rod from its lowermost position illustrated in FIGURES 8 and 9 wherein further downward movement of the piston rod is limited by the engagement of the bellows rod flange 194 with the spring retainer ring 187, and prevents flow of fluid from within the passage 176 to a closed charge chamber 204 of the housing. The charge chamber is provided by the connector housing section, a chamber housing section 205 whose lower end is threaded on the upper reduced portion 206 of the connector housing section, and the top housing section 207 whose reduced lower end portion 208 is threaded in the top end portion of the chamber housing section. An O-ring 21 0 seals between the connector and chamber housing sections and a similar O-ring 211 seals between the top and chamber housing sections.

A variable resistance assembly 215 is mounted in the charge chamber 204 and includes a non-conductive outer tube 216 of an electrically non-conductive substance, such as ceramic or the like, Whose upper end portion is rigidly secured, as by an adhesive or the like, in the downwardly opening central bore 217 of the top housing section 207. An inner non-conductive tube 218 is telescoped in the outer tube and is secured thereto, as by an adhesive, bonding or the like. 7

A resistance wire 220 is wound about the lower portion of the outer tube, its lower end being rigidly secured in a lateral bore 221 of the outer tube. The upper end portion of the wire extends upwardly through a suitable internal longitudinal slot 223 of the outer tube and then outwardly through a lateral aperture 225 of the outer tube into a longitudinal external slot 226. A contact screw 228 threaded in a suitable bore of the top housing section has an inner end which extends into the external slot and in electrical contact with the upper end of the resistance wire. It will thus be seen that the upper end of the resistance wire 220 is grounded to the transducer housing, and, therefore, to the tubing section 32 and thus to the producing flow conductor.

A sliding contact 230 is mounted on the upper end of a conductive leaf spring 231 Whose lower end is rigidly secured by means of screws 233 to an insulator ring 234 disposed on the upper reduced end portion 235 of the bellows rod.

The sliding contact is connected to the conductor 136, and, therefore, to one side of the solenoid coil 128, by a connector 236 having an outer tubular body 237 whose threaded portion 238 is threaded in a longitudinal passage 239 of the top housing section. The connector body has an O-ring 240 which seals between the top housing section and the connector body. The connector includes a conductor 241 which extends through its body and is insulated therefrom. The lower end of the conductor 136 is connected to the upper end of the conductor 241 and a conductor 242 connects its lower end to the leaf spring 231. It will be apparent that one end of the solenoid coil 128 is connected through the contact 230, the resistance wire 220, and the transducer housing to the production flow conductor. It will be apparent that the resistance wire 220 and the variable contact 230 constitutes a variable resistance 243 whose valve decreases as the contact moves upwardly on the wire.

The contact in turn is moved upwardly as the pressure in the flow conductor increases and causes the bellows assembly to contact, the greater the flow conductor pressure the greater the degree of contraction of the bellows assembly until it reaches its fully contracted or collapsed condition.

The other conductor 135, connected to the other end of the solenoid coil 128, extends to the surface through a suitable sealed aperture in the casing head to a control housing 244 and to one terminal 245a of a bellows switch 245. The other terminal 24512 of the switch 245 is connected to the movable or slidable contact 246 of a variable resistance 247 which is connected to a positive side of a source of electric current such as a battery 248 by a manually operated switch 249. The other side of the battery is grounded to the production flow conductor 22 so that it is connected through the flow conductor and the transducer housing to one side of the resistance wire 220.

It will thus be apparent that when the switches 245 and 249 are closed, the solenoid coil 128 is connected across the source of current 248 and when the value of the current flowing through the coil 128 increases to a predetermined value, the solenoid armature 101 will be raised upwardly to communicate the pressure from the annulus to the chamber 100.

The switch 245 has a contact 250 mounted on a bellows rod 251 which is biased to position wherein the movable contact is in the closed position in contact with the stationary contacts 245a and 245b illustrated in FIGURE 2 by the force of a spring 254 and the force of the pres sure of a charge of gas in the chamber 255 of a bellows 256. The bellows is mounted in a dish-shaped housing 259 having an aperture 261 through which the bellows rod extends slidably. An O-ring 263 disposed in a suitable annular recess of the bellows housing seals between the rod and the bellows housing. The resilient bellows 256 is of the usual tubular corrugated form having one end thereof secured to the front wall 265 of the housing by silver solder and the like which provides a hermetic seal therebetween so that a charge of gas under pressure introduced into the bellows chamber through a port 266 closed by a suitable plug 267 will bias the bellows toward its extended position. The other end of the bellows is secured similarly to the intermediate annular flange 268 of the bellows rod. One end portion of the spring bears against the annular shoulder 270 of the bellows housing located outwardly of a spring retainer annular flange 271 of the housing and its other end bears against the annular shoulder 274 of an annular end flange 275 rigidly secured to the bellows rod. The movement of the bellows rod toward a cap 276 threaded on the open end of the housing is limited by one or more spaced lugs 277 of the cap. A suitable gasket 279 seals between the cap and the housing.

A conduit 280 having an end portion telescoped in a passage 281 of the cap and secured in seal tight relationship thereto, as by silver solder, transmits the pressure from the upper closed end of the flow conductor 22 to the interior of the housing and thus to the exterior of the bellows. As a result when pressure at the upper end of the flow conductor 21 increases sufliciently to overcome the force exerted on the bellows rod by the force of the charge of gas in the bellows chamber and the force of the spring 254, the bellows rod is moved outwardly of the housing thus causing the switch 245 to open.

In use, the transducer 26 and the main valve 25 are mounted on a tubing section which constitutes a portion of the production flow conductor 22. One or more conventional gas lift valves 27 may be mounted at vertically spaced locations on the production flow conductor to permit injection of lift gas from the annulus into the production flow conductor at such locations. At the initiation of operation of the well installation, well fluids are usually present in both the annulus A above the packer 23 and in the production flow conductor to a considerable height above the main valve 25. In order to remove the well fluids from the annulus and the production flow conductor to the level of the main valve, the lift gas, which may be nitrogen or the like, under relatively high pressure is introduced into the annulus through the inlet conduit 28 from any suitable source. The gas lift valves 27 open at successively lower gas lift pressures, the highest valve 27 requiring the highest gas lift pressure to open, in the usual well known manner to lift successive columns or slugs of the well fluids to the surface until the well fluids to the level of the input ports of the lowermost valve 27 have been removed. The well fluids in the annulus are, of course, moved through the valves 27 into the flow conductor and the pressure of the lift gas is reduced successively as the well fluids are removed from the well so that the valves 27 will successively close as the well fluids are removed from the annulus and the flow conductor about each such valve 27. The lift gas pressure is then set at such low value that all the valves 27 will remain closed during further operation of the well installation. At this time, well fluids may still be present in the annulus to the level of the lowermost gas lift valve 27 The closure member 50 of the main valve 25 is now in its upper closed position since the armature ltll is in its lower position and the force of the fluid pressure from the tubing section 32 which is now communicated to the chamber is not sufficiently great to move the closure member downwardly against the resistance of the spring 77. Since only a very small area of the armature, the area within the line of sealing engagement of the armature seat with the seat ring 113, is exposed to the annulus pressure, the force of the annulus pressure cannot move the armature upwardly to its open position.

The switch 249 is then closed and the slidable contact 246 of the variable resistance 247 is movedto reduce the value of the variable resistance to such point that the current flowing in the electric circuit which includes the serially connected variable resistance 247, the solenoid coil 128 and the variable resistance 243, regardless of the location of the slidable contact 230 on the resistance wire 220, is eflective to raise the armature to its open position. As the armature is moved to its upper position, the pressure of the lift gas in the annulus is communicated to the chamber 100 and is effective to move the closure member downwardly to its open position; and, since the pressure of the lift gas in the annulus is considerably greater than the pressure within the flow conductor at the location of the main valve, the lift gas will cause the well liquids in the annulus above the valve ports 47 to flow through the valve ports into the valve housing and thence into the production flow conductor. The bellows switch 245 is now closed since the pressure in the upper end of the flow conductor at the location of the conduit 280 is low, for example, at atmospheric pressure if the discharge end of the flow conduit 30 opens to the atmosphere. When the level of the liquids in the annulus drops below the ports 47, the lift gas flows into the production flow conductor and moves the column of liquids above the port 37 of the tubing section 32 to the surface. As the column of well liquids reaches the upper end of the production flow conductor and moves into the flow conduit 30, the pressure within the bellows housing 258 increases sharply to that of the well liquids flowing into the flow conduit 30, and is effective to move the bellows rod outwardly opening the bellows switch. When the bellows switch opens, the solenoid coil 128 is dcenergized and the armature is moved back to its closed position by its own weight andthe force of the spring 140. The pressure in the chamber 100 now decreases to that in the tubing section 32 at its port 156, and the force of the spring 177, as well as the force of the pressure diflerentlal existing across the closure member, is effective to move the closure member back upwardly to its closed position. The flow of lift gas from the annulus into the production flow conductor is thus stopped at the time the top end of the column of well liquids reaches the upper end of the production flow conductor 22. The expansion of the lift gas in the flow conductor below such column of well liquids, however, expels the column of well llqulds from the flow conductor into the flow conduit.

With the annulus now free of well liquids to a level below the ports 47, the well installation is in condition to operate periodically to move the column of well liquids whichaccumulate in the production flow conductor above the port 37 as such'column attains a predetermined height. The bellows assembly 180 of the transducer contracts as such column increases in length above the tubing section 177. Theadjustable contact of the variable resistance at the surface is then moved to set the value of such variable resistance at such a value that, as the column of well fluids in the production flow conductor above the main valve increases in height and the hydrostatic pressure at the port 36 is thus gradually raised, the bellows assembly 180 of the transducer contracts gradually so that the contact 230 is moved upwardly gradually on the resistance wire 220 to a position wherein the combined resistance of the two variable resistances is so low that the current flowing in the solenoid coil is effective to move the armature 101 upwardly. when the fluid column attains such predetermined height. The column or slug of well liquids is then moved upwardly by the lift gas flowing into the production flow conductor until the bellows switch 245 is opened, as the top end of the column reaches the upper end of the flow conductor, and the main valve is closed.

The expansion of the lift gas in the flow conductor then causes the fulltcolumn to be expelled from the flow conductor and into the flow conduit. As the well fluids are expelled from the flow conduit, the bellows assembly 180 contracts since the pressure in the flow conductor is reduced or drops, and the movable contact is moved downwardly on the resistance wire. As the pressure at the upper end ofthe flow conductor drops, the bellows switch is closed. Closure of the bellows switch will not now again cause the solenoid armature to be moved to its upper position since the transducer bellows assembly has now contracted and the value of the variable resistance 243 is again high.

This sequence of operations of the main valve, transducer and bellows switch is repeated each time the well liquids in the flow conductor accumulate to the predetermined height in the flow conductor above the transducer and the main valve and are moved out of the flow conductor and into the flow conduit.

The height of the column of well fluids at which the main valve opens may be varied merely by varying the position of the adjustable contact 246 of the variable resistance 247. It will thus be apparent that the operation of the main valve may be controlled or adjusted at the surface to obtain most eflicient production of well fluids with the expenditure of minimum volumes of the lift gas.

It will further be seen that such adjustment may be made initially to obtain the most eflicient operation at the initiation of operation of the production. and may thereafter be changed as required by the changing characteristics, such as a pressure or rate of flow of the well fluids from a production formation.

It will be apparent that the use of the bellows operated switch 245, the expenditure of the lift gas is minimized, since as soon as the column of well liquids reaches the flow conduit 30, the introduction of the gas into the production flow'conductor is arrested and the expansion of the gas previously injected into the production flow conducter of the column of liquids completes the movement of the production flow conductor into the flow conduit 30.

If desired, the bellows operated switch 245 may be omitted, as illustrated in FIGURE 10, in which case the solenoid armature will be raised and the valve 25 opened when the column of well liquids attains a predetermined height above the main valve and will close when the pressure within the production flow conductor drops to a value somewhat below that at which the valve is opened because the current flowing through the solenoid coil necessary to move the armature to its open position is greater than the value thereof necessary to hold it in its upper position. This spread between the opening and closing pressures may be controlled by the selection of a solenoid having the proper spread between the armature moving and armature holding values of the electric current flowing through its coil 128.

It will be apparent, of course, that the solenoid coil and the top housing section 104 are formed of a suitable non-magnetic substance, such as brass, and that the armature is formed of a magnetic substance such as iron.

It will now be seen that a new and improved well installation has been illustrated and described wherein the injection of the gas into the production flow conductor is determined solely by the pressure within .the flow conductor adjacent the location of injection and, therefore, solely by the height of the column of well fluids in the flow conductor above the location of injection.

It will also be seen that the value of the flow conductor pressure at the location of injection necessary to cause such injection of gas into the flow conductor can be varied at the surface of the well so that most efficient production of well fluids may be obtained.

It will also be apparent that a new and improved electrically operated valve has been illustrated and described for use in a. well installation to inject gas into a production flow conductor to facilitate flow of well fluids therethrough.

It will further be seen that the electric valve includes a closure member, means biasing the closure member to closed position, and electrically operable means for communicating the pressure of the lift gas to the piston means of the closure member to move the closure member to open position when the electrically operable means is energized with electric current of a predetermined value.

It also will be seen that a new and improved transducer has been illustrated and described which is responsive to the pressure within the flow conductor for causing the current flowing to the electrically operable means of the valve to vary in accordance with the fluid pressure within the flow conductor.

It will also been seen that the transducer includes a bellows assembly which contracts and expands in accordance with the fluid pressure in the flow conductor to vary the effective value of a variable resistance of the transducer connectible in the electric circuit of the electrically operable means of the valve ot cause the current flowing in such circuit to vary inversely as the fluid pressure in the flow conductor at the location of the transducer.

It will further be seen that while the valve and the transducer have been illustrated and described as being separate devices each having its own housing, that the transducer and the valve could, if desired, be housed in one common housing.

Referring now particularly to FIGURES 11, 12 and 13 of the drawings, the well installation may be used to produce fluids from the wells where it is desirable that the lift gas be injected through the lowermost valve 2511 under relatively high pressure, it being apparent that in the well instalaltion 20 the pressure of the lift gas during the normal operation of the installation, after the well fluids have been unloaded by the operation of the unloading valves 27, must be lower than the pressure at which the lowermost unloading valve 27 opens. As a result, the pressure of the lift gas during the normal operation of the well installation 20 is considerably lower than the maximum pressure available.

Elements of the well installation 20a, have been provided with the same reference numerals, to which the subscript a has been added, as the corresponding elements of the well installation 20.

The flow conductor 22a has a plurality of spaced tubing sections 32a, 32b 32n connected therein at longitudinally spaced locations, each of which has a transducer 26 and a valve 25 mounted thereon so that gas may be injected from the annulus into the flow conductor at any one of a plurality of longitudinally spaced locations de pending on which of the valves has its coil 128 energized. The transducer 260 is identical to the transducer 26 but the transducer 26b mounted on the flow conductor section 32b differs from the transducer 26 by having a contact 301 below the lower end of the resistance wire 220 thereof so that when the pressure in the tubing in the flow conductor at the location of the transducer 26b is below a predetermined value, and its bellows assembly 180 is in its contracted condition, its movable contact 23% engages the contact 301. The contact 301 is connected by a conductor 302 to a conductor 303 of the connector 13617. A shunt conductor 307 connects the upper end of the conductor 303 to one side of the coil 128b of the valve 26b, the opposite end of the coil being connected to thec ontact 230. Each transducer of the well installation 20a, except the lowermost transducer 26a, has the same structure as the transducer 261; and its contacts 301 and 230 are similarly conected to opposite ends of the coils of the valve whose operation is controlled thereby.

The coils of the valves are connected in series to one side of the battery 248a through the manually operated main switch 249a, the variable resistance 247a, the bellows operated switch 245a, and the conductors 310 and 311n 311a. Each valve is connectable to the other side of the battery 248a when the bellows of its associated transducer 26 is in at least partially contracted position so that its contact 230 thereof is in engagement with the resistance wire 220 thereof through its contact 230, its resistance wire 220 and ground. When the bellows of a transducer 26b 26n is in its contracted position, no or little current will flow through the coil of its associated valve since it is then shunted or short circuited by a shunt conductor 307. For example, as illustrated in FIGURE 13, if a relatively low pressure is present in the flow conductor at the location of the transducer 2611, its contact 230n is in engagement with its contact 301n so that its coil is shunted or short circuited, and no current will flow through the coil 12811 of the valve 25n which thus will remain closed even if the manual switch 249a is closed. If at this time a column of liquids is present in the flow conductor above another lower valve such as the valve 2511, so that the contact 230b of its associated transducer is in engagement with its resistance 220n, the coil 1281: of its valve 25b will be energized and the valve 25b will be open. At this time, since the contact 230 of any transducer below the valve 25b, such as the transducer 26a, will also be in its upper position on its resistance Wire 220a. The coil 128a however will not be energized, since the resistance between the contact 23% and the battery 248 through ground is relatively low. If such resistance is relatively great, suflicient current may also flow through the coil 128a of the valve 25a and it will also be open but this will not interfere with the operation of the well installation as will be explained below.

In use, at the time of initiation of the operation of the well installation 20a, well fluids are usually present in both the annulus A above the packer 23a and in the production flow conductor to a considerable height above the lowermost valve 25a. For example, well fluids may be present in the annulus and the production flow conductor to a considerable height above the top valve 25n and its associated transducer 2611. The bellows of all of the transducers are now in their fully contracted positions so that one side of each valve is now connected to one side of the battery 248a through its contact 230, a very small portion of its resistance wire 220 and ground. The other side of the coil 12811 of the top valve 25n is then connected to the other side of the battery 248 through the closed bellows switch 245a, the variable resistance 247a and the manually operated main switch 249a. The other sides of each of the other coils of the other valves are similarly connected to the other side of the battery through the coils of the valves disposed thereabove. The top valve is now open, and depending on the value of the voltage of the battery and the effective resistance of ground between the battery and their resistance wires 220, one or more next lower valves may also be open. The lift gas, which may be nitrogen or the like, is then introduced under high pressure into the annulus through the inlet conduit 28a from any suitable source. Since at least the top lift valve 25n is now open, the lift gas introduced into the annulus causes the well fluids in the annulus to flow through the top valve 2511 into the production flow conductor and thence outwardly to the surface. When the level of the well fluids in the well has dropped to the level of the top valve 25n, the column of fluids above its transducer 26n is of very short height and the bellows will now be in fully expanded position and its movable contact 230a will now be in contact with its stationary contact 301n. As a result, since the shunt conductor 307 is now connected across the coil 128, no current will flow through the coil 128n and the valve will close. The valve 251?, if it has not been open will now open once the impedance of the coil 128n is shunted from the circuit of its coil 128n so that continued injection of the gas at the same high pressure will cause the well fluids in the annulus above the valve 25b to flow through the valve b into the flow conductor and thence upwardly to the surface. As the slug of well fluids moves upwardly through the section 32n of the flow conductor, the pressure at the transducer 26n will, of course, increase and the valve 25n may again open to permit flow of gas into the flow conductor below the slug of well fluids to further facilitate the upward flow of well fluids therethrough. When the well fluids in the annulus have been removed to the level of the lowermost or main valve 25a by the successive operation of the valves located thereabove, the valve 25a will open each time a column of well fluids accumulates to a predetermined height in the production flow conductor in the same manner as previously described in connection with the valve 25 of the well installation 20. During the unloading stage of operation of the well installation, the bellows operated switch 245a may be held closed by shutting a valve 314 connected in the conduit 280a.

If it is desired that only one valve 25 be open at any one time, the force exerted by the biasing spring 186 of each valve may be adjusted to be greater than that of the next lower valve so that each valve will open when a column of well fluids is present thereabove in the flow conductor of smaller height than that necessary to be present above the next higher value to cause such next higher valve to open.

It will now be apparent that the well fluids present in the flow conductor, and perhaps in the annulus, of the well installation may be unloaded, if desired, by using lift gas under highest available pressure and that the subsequent normal operation of the lowermost valve 25a may also be by use of lift gas of any desired pressure, the normal operation of the valve 25a being responsive only to a predetermined height of well fluids present in the flow conductor thereabove and closing each time such column reaches the top end of the flow conductor and the bellows operated switch 245a opens.

Referring now to FIGURES l4 and 15 of the drawings, the well installation 20b may be used in locations where the rate of supply of the lift gas may be limited; as, for example, in locations wherein a single source of the lift gas must supply several well installations and wherein the annulus A of each well installation constitutes a reservoir for such lift gas. At such installations, it is desirable for proper efficient operation of the apparatus that the valves 25 open only when the pressure in the annulus attains a predetermined value since at certain times the pressure of the lift gas in the annulus may be too low for efficient operation even though the height of the column of fluids in the flow conductor above a valve 25 is sufficiently high that the bellows of the transducer which controls operation of the valve is in contracted position. The housing 25912 of the bellows operated switch 245b is connected to the gas inlet conduit 28b downstream of the usual choke or restriction 351 provided therein. The pressure of the lift gas in the gas conduit 28b downstream of the choke 351 is communicated to the bellows housing 25% by the conduit 280b. The movable contact 25% is positioned to move into its closed position and in engagement with the stationary contacts of the switch when the pressure in the annulus reaches a predetermined value and to move to its open position when the pressure drops below the predetermined value.

The operation of the well installation 2011 is responsive not only to the column of well fluids above a valve 25 thereof but also to the pressure of the lift gas in the annulus A, so that a valve 25 will open only when a column of well fluids in the flow conductor thereabove has attained a predetermined height and the bellows assembly of its transducer has contracted to move its contact 230 to its appropriate location on its resistance wire 220, and the pressure in the annulus '-A is above the predetermined value and the switch 245b is closed.

It will thus be apparent that any valve 25 which opens will remain open until the slug of liquids thereabove is moved upwardly and outwardly to the conduit 30b and the pressure within the flow conductor decreases as the slug is discharged into the conduit 30b.

Referring now particularly to FIGURE 16 of the drawings, the well installation 200 may be used to produce fluids from wells where it is desirable that the injection of the lift gas be continuous for optimum economy of gas usage and optimum production of well fluids and Where it may be desirable to change the location of injection of the gas into the flow conductor as the well conditions change, as for example, when the pressure of the well fluids from at producing earth formation declines or when the characteristics of the well fluids being produced change. 'For example, the proportion of gas and liquid, or the proportion of different liquids, such as oil and water, being produced from the earth formation may change.

The well installation 20b includes a flow conductor 400 having a plurality of valves 25a, 25b, and 250, each identical to the valve 25 of the well. installation 20, mounted thereon in longitudinally spaced locations above a packer 402 which seals between the flow conductor and the well casing 403. Conventional gas lift valves 27 may also be mounted above the gas lift valves. The gas inlet conduit 28c has connected therein a suitable pressure regulator valve 401 of any suitable well known type, such as the one illustrated on page 3730 of the Composite Catalogue of Oil Field Equipment and Services, 1965-66 edition, which operates to maintain the pressure in the annulus from rising above a predetermined adjustable value. The coils 128a, 128b, and 128s of the valves have one side grounded to the flow conductor and their other sides connected by conductors 404a, 4041) and 4040 and manually operated switches 405a, 4051: and 405e, respectively, to one side of a source of current or battery 406 whose other side is grounded to the flow conductor.

It will be apparent that upon the initiation of operation of the well installation 20c, gas under pressure is admitted into the annulus and the conventional unloading valves 27 operate in the usual way until any well fluids present in the annulus and in the flow conductor above the lowermost valve 27 has been removed. If it is then desired to inject gas into the flow conductor through the highest valve 250, it is opened by closing its associate switch 405a, and the pressure regulator valve 401 is set to maintain the pressure in the annulus at a predetermined value so that once any well liquids present in the annulus when the valve 250 has been moved by the gas into the flow conductor through the valve 250, gas is injected into the flow conductor continuously at a predetermined rate to facilitate the flow of the well fluids through the flow conductor to the surface. Should the well conditions change and it is desired to inject gas at a different location such as through the valve 25b, the switch 405c is opened and the switch 40512 is closed. The rate of injection of gas into the flow conductor at any selected valve 25a, 25b, or 25c may, of course, be selected by adjusting the pressure regulator valve to maintain the pressure in the annulus at a predetermined value.

It will now be seen that the electric valves may be employed in a well installation to control the injection of gas therethrough into a flow conductor with theoperation of the valve being controllable either by a transducer which is responsive to the height of a column of well fluids in the flow conductor above the transducer and the valve as in the case of the well installations 20, 20a and 20b or, as in the case of the well installation 200, may be controlled solely at the surface by means of switches.

It will further be seen that while in the valve installation 200 has been shown as being in use in a continuous gas injection type well installation, the switch of a particular selected valve may be operated periodically to provide for intermittent injection of gas where the supply of gas is sufiicient to permit such intermittent operation.

It will further be seen that while in the well installations 20, 20a and 20b the transducer and valve have been shown as having separate housing, both. the transducer and the valve, if desired, could be mounted in a common housing.

The foregoing description of the invention is explanatory only, and changes in the details of the construction illustrated may be made by those skilled in the art, within the scope of the appended claims, without departing from the spirit of the invention.

What is clamed and desired to be secured by Letters Patent is:

1. A well installation including: a production flow conductor through which well fluids are transportable to the surface of the well; means providing an annulus about the production flow conductor closed above the bottom end of the flow conductor into which lift gas under pressure may be introduced; electrically operable valve means mounted on said flow conductor for controlling injection of lift gas into said flow conductor from said annulus; first electric control means on said flow conductor responsive to fluid pressure in said flow conductor for causing said valve to open to permit lift gas from the annulus to flow into the flow conductor to lift a column of well fluids above said valve means to the surface; and second electric control means operately associated with said valve means and said first control means and selectively adjustable at the surface of the well for varying the response of said first control means to the fluid pressure in said flow conductor to control the actuation of said valve means.

2. A well installation including: a production flow conductor through which well fluids are transportable to the surface of the well; means providing an annulus about the production flow conductor closed off above the bottom end of the flow conductor into which lift gas under pressure may be introduced; valve means mounted on said flow conductor for controlling injection of lift gas into said flow conductor from said annulus; electrically operable means for opening said valve when the g electric current flowing through said electrically operable means attains a predetermined value; first electric control means on said flow conductor responsive to fluid pressure in said flow conductor for causing said valve to open to permit lift gas from the annulus to flow into the flow conductor to lift a column of well fluids above said valve means to the surface; second electric control means at the surface of the well operatively associated with said first electric control means and selectively adjustable at the surface of the well for varying the response of said first control means to the fluid pressure in said flow conductor to control actuation of said electrically operable means for opening said valve means to control the pressure at which said first electric control means causes said valve means to open; said first control means including: a transducer having a variable electric resistance which varies in accordance with the pressure within said flow conductor adjacent said valve means, said variable resistance being connected in an electric circuit with said electrically operable means of said valve for causing the resistance of said electric circuit to decrease and the current flowing through said electrically operable means to increase as the pressure in said flow conductor increases adjacent said valve means.

3. The well installation of claim 2, wherein said second control means comprises a variable electric resistance connected in said electric circuit.

4. The well installation of claim 3, and means responsive to the pressure in said flow conductor at the surface of the well for de-energizing said electric circuit to cause said valve means to close when the pressure in the upper end of said flow conductor increases as the column of well fluids reaches the surface.

5. The well installation of claim 2 wherein said transducer comprises a pressure responsive mean-s movable in one direction by fluid pressure in the flow conductor; means biasing said pressure responsive means in a sec-ond direction opposite said one direction; and means operatively associated with said pressure responsive means and said variable resistance of said transducer for decreasing the value of said variable resistance as said pressure responsive means moves in said one direction and for increasing the value of said variable resistance as said pressure responsive means moves in said second direction.

6. The well installation of claim 5, wherein said valve means comprises a housing providing a front passage between the interior of a flow conductor and said annulus; a closure member movably mounted in said housing for closing said passage; means biasing said closure member to closed position; pressure responsive means for moving said closure member to open position, said housing having a second passage for admitting the pressure from the annuluus to said pressure responsive means to cause said closure member to move to open position;

16 and electrically operable means for closing said second passage.

7. The well installation of claim 6, wherein said electrically operable means comprises a solenoid having a coil connected in an electric circuit with said variable resistance of said transducer, and an armature movable to open said second passage when the current in said coil rises to a predetermined value.

-8. The well installation of claim 7, wherein said second control means includes a variable resistance.

9. The well installation of claim 8, and means respon sive to the pressure in the upper portion of the flow conductor for de-energizing said coil when the pressure in the upper portion of the flow conductor exceeds a predetermined value.

10. A valve for injecting gas into a flow conductor, said valve including: a housing mountable on a flow conductor and having a first passage for communicating the exterior of the housing with the interior of a flow conductor on which it is mountable; a closure member m0vably mounted in said housing and biased in one direction toward position closing said passage, said housing means having a chamber; pressure responsive means movable in said chamber and operatively associated with said closure member for moving said closure member in a second direction opposite said one direction, said housing having a second passage for communicating pressure from the exterior of the housing to said chamber and a third passage for communicating the interior of a flow conductor on which said housing is mountable with said chamber, electrically operable means having closure means movable between 21 first position wherein said closure means opens said second passage and closes said third passage to cause pressure from the exterior of said housing to be communicated to said chamber and said pressure responsive means to cause said closure member to move to open position and a second passage and opens said third passage to permit fluid pressure in said chamber to vent to the interior of said flow conductor and permit said closure means to move to closed position.

11. The valve of claim 10, wherein said electrically operable means includes a solenoid having a coil and an armature movable from said first position to said second position by said coil when said coil is energized with current of a predetermined value.

12. The valve of claim 11, wherein said pressure responsive means comprising piston means secured to said closure member.

13. The valve of claim 12, wherein said armature is provided with seat means for closing said second and third passages.

14. The valve of claim 11, wherein said armature is provided with seat means for closing said second and third passages.

15. A transducer usable to control operation of a valve used to inject gas into a flow conductor, said transducer including: a housing mounted in a flow conductor, a pressure responsive means mounted in said housing and exposed to prepared from within said flow conductor when said transducer is mounted on said flow conductor; electric resistance means in said flow conductor, and means movable by said pressure responsive means and operatively associated with said resistance means for varying the resistance of said reistance mean in accordance with the pressure in said flow conductor.

16. The transducer of claim 15, wherein said pressure responsive means includes a bellows, a bellows rod movable by said bellows, and means biasing said bellows rod in one direction toward one external position in said housing, pressure in the flow conductor tending to control said bellows and move said bellows rod in a second direction opposite said one direction.

17. The transducer of claim 16, electric resistance means mounted in said housing, and a contact mounted on said bellows rod and movable on said resistance means to decrease the effective value of said resistance means in accordance with the movement of said bellows rod in said second direction.

18. Well installation of claim 3 and means responsive to the pressure in one of said annulus and said flow conductor for preventing energization of said valve means when the pressure in said one of said annulus and said flow conductor is not at a predetermined value.

19. The well installation of claim '3 and means responsive to the pressure in the annulus for preventing energization of said valve means when the pressure in the annulus is below a predetermined value.

20. A well installation including: a production flow conductor through which well fluids are transportable to the surface of the well; means providing an annulus about the production flow conductor closed above the bottom end of the flow conductor into which lift gas under pres sure may be introduced; electrically operable valve means mounted on said flow conductor for controlling the injection of lift gas into said :fiow conductor from said annulus; first electric control means on said flow conductor electrically connected with said electrically operable valve means and responsive to fluid pressure in said flow conductor for actuating said valve means to open said valve means to permit lift gas from the annulus to flow into the flow conductor to lift a column of well fluids therein; and second electric control means at the well surface operatively connected with said first electric control means and selectively adjustable at the surface of the -well for varying the response of said first electric control means to the pressure in said flow conductor to control the actuation of said electrically operable valve means by said first control means, whereby the pressure to which said first control means is responsive to cause actuation of said valve to open position may be variably controlled from the surface.

21. The well installation of claim 20 wherein said first electric control means, and said second electric control means, com-prise variable electrical resistances for controlling the actuation of the electrically operable valve means by electric current flowing through said resistances.

22. The well installation of claim 20 wherein said valve means comprises a plurality of valves spaced longitudinally of said flow conductor and wherein said electric control means includes switch means at the surface of said well operable to open any selected one of said valves.

23. The well installation of claim 21 wherein said valve means comprises the plurality of valves spaced longitudinally of said flow conductor and said control means includes means responsive to the pressure within the flow conductor adjacent each of said valves.

24. The well installation of claim 1 wherein said valve means comprises a plurality of valves spaced longitudinally of said flow conductor and wherein said control means includes individual control means operatively associated with each of said valves and responsive to the pressure adjacent each of said valves for causing energization of said electrically operable means to cause the said valves to open whenever the pressure adjacent any one of the valves exceeds a predetermined value within the flow conductor.

25. The well installation of claim 23 wherein said control means includes means responsive to the pressure in said flow conductor at the surface of the well installation of the well for preventing energization of said electrically operable means of the valves when the pressure in said flow conductor is below a predetermined value.

References Cited UNITED STATES PATENTS 2,658,460 11/1953 Davis 103-233 2,703,532 3/1955 Bobo 103-232 X 2,725,014 11/1955 Pryor 103-233 2,869,475 1/1959 Bobo 103-233 2,876,434 3/1959 Oberlin 103-233 X DONLEY I. STOCKING, Primary Examiner. WARREN J. KRAUSS, Assistant Examiner.

US. Cl. X.R. 137-155 Patent No.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Dated February 18, 1969 C01. 2, line 14, C01 2, line 60, for C01. 8, line 13, C01 9, line 40, after Col. 11, line 3, Col. 11 line 17, for Col. 11 line 49, for Col. 14, line 66, for C01. 15, line 74, for Col 16 line 59, for Col 16 line 64, for C01 16, line 64, for

(SEAL) Am Edwudllflmhqlr. Attosting 0mm- It: is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

for "anther" read --another- "instalaltion" read --installation-- for "21" read --22-- "contact" insert --247-- for "0t" read --to-- "instalaltion" read --insta1lation-- "thec ontact" read -the contact-- "clamed" read --c1aimed-- "annuluus" read --annu1us-- "prepared" read --pressure-- "reistance" read --resistance-- "mean" read --means-- SHQZQED AND SEALED MAR 3 H970 WILLIAM 3. 50mm. JR. Oomissioner 01' Patent: 

